The invention relates to a power transmission having one or more clutches in such a way that the driven part is delayed with respect to the driving part in a substantially non-slip synchronous run or can be completely stopped despite a continuously further running driving part. Thus, with the driving part several driven parts can be driven and delayed or stopped independently of one another.
The construction according to the invention is particularly suitable for the transmission of low forces or driving torques, such as occur in adjusting devices, which are used for the positioning or position-adjustment of units, e.g. the working units of machines. Such working units are initially set up without working engagement and are only brought into the latter in the set and optionally fixed position. For a precise setting it is advantageous if the power transmission or the unit in the regulating movement can be interrupted or stopped substantially free from any delay or transition, e.g. in such a way that the frictional or mass forces have no effect and the unit, despite the interruption of the power transmission, still lags over a delay path.
Independently of its use, the clutch must be constructed in the manner of an overload protector responding to a driving torque, so that the driving torque transferred by it for release purposes does not, in the manner of a locking clutch, briefly significantly rise and instead has at the most a limited or no rise or with response immediately decreases in a substantially transition-free manner.
In the case of machines for machining flat substrates or webs, such as paper, cardboard, etc., the latter are e.g. drawn continuously from storage reels and subdivided into individual units, e.g. Juxtaposed running longitudinal webs and/or successively running individual layers, the most varied working units, such as devices for producing cuts, grooves, perforations, for separating or flush abutment of adjacent or stacked individual units, for longitudinal and/or transverse supply of substrate strips, for conveying, cambering, stop limitation or the like are usable and in each case act on a single unit or simultaneously on a plurality of such units, which are e.g. connected to one another in a ragged flow or in reciprocal engagement in a strand. These devices usually operate in the area of longitudinal edges or borders of the substrate web parallel to the running direction and are settable or adjustable for format change. purposes transversely to the running direction and roughly parallel to the running plane, a setting accuracy of below 2 or 1 or 1/2 mm being advantageous.
If the adjusting device has an adjusting spindle with an adjusting nut and the latter is fixable with respect to the working unit with a clamping device, as well as being releasable for free rotation with the spindle, during release and as a result of its inertia it requires an acceleration time until it rotates synchronously with the adjusting spindle and consequently no longer transfers an adjusting movement. This can lead to a significant reduction in the adjusting accuracy. The situation is similar with respect to delays on fixing the spindle nut relative to the working unit. In the case of a released and synchronously rotating spindle nut no adjusting force acts on the working unit, so that a resetting of the adjustment position of the working unit is only possible by again fixing the spindle nut. However, if the spindle nut is not released as a result of a malfunction, then on the working unit the adjusting force continues to act in the manner of a positive drive if said working unit runs up onto an obstacle, e.g. a machine frame and considerable damage can occur.